JP2005019221A - Fuel cell system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To efficiently generate power with a simple and compact structure. <P>SOLUTION: An ejector 36 for sucking exhaust gas from a fuel gas circulating passage 30 and returning it to a fuel cell stack 12 is disposed in a fuel gas supply passage 28. A heat exchanger 38 for vaporizing moisture which is contained in the exhaust gas and has passed through the ejector 36 is disposed between the downstream of the ejector 36 and the fuel cell stack 12. In this heat exchanger 38, the exhaust gas supplied from the fuel cell circulating passage 30 is used as a medium to be heated (heat source), on the other hand, compressed air supplied from an oxidant gas supply passage 31 is used as a heating medium, and the exhaust gas is heated by this compressed air. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention provides a fuel gas supply channel for supplying fuel gas to a fuel cell, and an exhaust gas containing unused fuel gas discharged from the fuel cell by an ejector provided in the fuel gas supply channel. The present invention relates to a fuel cell system including a fuel gas circulation channel for returning to the middle of a gas supply channel and supplying the fuel cell.
[0002]
[Prior art]
For example, in a polymer electrolyte fuel cell, an electrolyte membrane / electrode structure in which an anode electrode and a cathode electrode are arranged on both sides of an electrolyte membrane made of a polymer ion exchange membrane (cation exchange membrane) is sandwiched between separators. is doing. This type of fuel cell is normally used as a fuel cell stack by laminating a predetermined number of electrolyte membrane / electrode structures and separators.
[0003]
In a fuel cell, a fuel gas, for example, a hydrogen-containing gas, supplied to an anode-side electrode moves to the cathode-side electrode through an electrolyte membrane that is appropriately humidified and hydrogen is ionized on the electrode catalyst. Electrons generated during the period are taken out to an external circuit and used as direct current electric energy. Since an oxidant gas, for example, an oxygen-containing gas such as air, is supplied to the cathode side electrode, water is generated by the reaction of hydrogen ions, electrons, and oxygen gas at the cathode side electrode.
[0004]
This type of fuel cell employs a fuel gas circulation fuel cell system that mixes exhaust gas containing unused fuel gas discharged from the fuel cell with newly supplied fuel gas and supplies the mixed fuel gas to the fuel cell. ing. This is because the consumption of fuel gas is saved and the hydrogen utilization rate is improved.
[0005]
By the way, in the fuel gas circulation type fuel cell system, the generated water generated in the fuel cell circulates in the fuel gas circulation system in a liquid state such as condensed water or mist. For this reason, liquid produced water may adhere to the anode side electrode of the fuel cell, and fuel gas may not be supplied to the anode side electrode.
[0006]
Therefore, for example, Patent Document 1 discloses a fuel cell power generator capable of preventing moisture contained in the fuel off-gas from condensing in the gas pipeline in a mixed state with the newly supplied fuel gas. Is disclosed. Specifically, as shown in FIG. 6, in the phosphoric acid fuel cell 1, a cooling plate 1c is interposed between a fuel electrode 1a and an air electrode 1b, and fuel gas is supplied to the fuel cell 1. A system 2, a reaction air supply system 3, and a cooling water circulation system 4 are connected.
[0007]
The fuel gas supply system 2 includes a fuel gas supply circuit 2a, a fuel off-gas recycle circuit 2b, and a mixed gas circuit 2c, and an ejector pump 5 is connected to a point where these join. The cooling water circulation system 4 includes a water vapor separator 4 a and a cooling water circulation pump 6.
[0008]
A gas heater 7 that functions as a heat exchanger is disposed in the mixed gas circuit 2c. The gas heater 7 includes a heating coil 7a wound around a pipe line of the mixed gas circuit 2c and extracted from the water vapor separator 4a provided in the cooling water circulation system 4 of the fuel cell 1. Steam is flowing as a heating medium.
[0009]
In such a configuration, during operation of the fuel cell 1, water and water vapor are stored in the water vapor separator 4a, and mixed with water vapor supplied from the water vapor separator 4a to the heating coil 7a of the gas heater 7. The fuel mixed gas is heated and heated by heat exchange with the fuel mixed gas flowing through the gas circuit 2c. For this reason, the relative humidity of the fuel mixed gas is lowered, and the operation of the fuel cell 1 is performed in a state where condensation of moisture contained in the fuel mixed gas is difficult to occur, and condensed water accumulates in the gas pipe. It is not.
[0010]
[Patent Document 1]
JP-A-8-321316 (paragraphs [0003], [0020] to [0021], FIG. 3)
[0011]
[Problems to be solved by the invention]
By the way, in the above Patent Document 1, since the operation temperature is maintained at about 180 ° C., even if mist is contained in the fuel off-gas supplied to the fuel cell 1, this mist is generated by the high-temperature fuel cell 1. Evaporates easily. Moreover, Patent Document 1 relates to the phosphoric acid fuel cell 1 and does not require humidification of the electrolyte.
[0012]
On the other hand, in the polymer electrolyte fuel cell, the solid polymer electrolyte membrane needs to be appropriately humidified in order to allow hydrogen ions to permeate from the anode side electrode to the cathode side electrode using moisture as a carrier. However, Patent Document 1 only needs to remove moisture contained in the fuel off gas, and there is a problem that the technique of Patent Document 1 cannot be directly applied to the polymer electrolyte fuel cell.
[0013]
The present invention solves this type of problem, and an object thereof is to provide a fuel cell system capable of performing efficient power generation with a simple and compact configuration.
[0014]
[Means for Solving the Problems]
In the fuel cell system according to claim 1 of the present invention, a fuel cell that generates power by being supplied with a fuel gas and an oxidant gas, a fuel gas supply channel that supplies the fuel gas to the fuel cell, and the fuel cell A fuel gas circulation channel for returning exhaust gas containing unused fuel gas discharged from the fuel gas to the fuel cell by returning it to the middle of the fuel gas supply channel by an ejector provided in the fuel gas supply channel And. A steaming mechanism is provided between the downstream of the ejector and the fuel cell to steam the water contained in the exhaust gas that has passed through the ejector.
[0015]
The ejector mixes new fuel gas flowing through the fuel gas supply channel with exhaust gas discharged from the fuel cell, and makes the generated water contained in the exhaust gas into a mist. Furthermore, the mist-like generated water is steamed through a steaming mechanism disposed downstream of the ejector.
[0016]
For this reason, mist-like produced water is supplied into the fuel cell and does not adhere to the anode side electrode, and the vaporized produced water permeates the anode side electrode well. Therefore, the fuel gas can be reliably supplied to the anode side electrode, and the desired power generation performance can be maintained. Moreover, the steamed product water can be used as the humidified water, and a dedicated humidifier is not required, and the product water is effectively used.
[0017]
In the fuel cell system according to claim 2 of the present invention, an oxidant gas supply channel for supplying an oxidant gas to the fuel cell is provided, and the oxidant gas supply channel is a heat exchange that constitutes a water vaporization mechanism. And a compressor for sending the compressed oxidant gas to the heat exchanger as a heat source in the oxidant gas supply flow path. .
[0018]
Since the compressor compresses an oxidant gas, for example, air, and supplies it to the fuel cell, the compressed air is at a temperature higher than the operating temperature of the polymer electrolyte fuel cell, for example. Therefore, by supplying high-temperature air (compressed air) as a heat source to the heat exchanger, the generated water is vaporized and the high-temperature air that is the oxidant gas is cooled. For this reason, a heat exchanger and a humidifier are integrated and size reduction of the whole fuel cell system is achieved easily. In addition, air can be heated quickly under the compression action of the compressor, the response of the heat exchanger can be effectively improved, and the generated water can be reliably vaporized immediately after operation of the fuel cell system. .
[0019]
The fuel cell system according to claim 3 of the present invention further includes a cooling medium circulation passage for circulating and supplying a cooling medium to the fuel cell, and the cooling medium circulation passage is discharged from the cooling medium outlet of the fuel cell. The cooling medium can be supplied as a heat source to the heat exchanger constituting the steaming mechanism. Thereby, the high temperature cooling medium discharged from the fuel cell is supplied to the heat exchanger as a heat source, whereby the generated water is vaporized and the high temperature cooling medium is cooled. Therefore, the heat exchanger and the humidifier are integrated, and the entire fuel cell system can be easily downsized.
[0020]
Furthermore, in the fuel cell system according to claim 4 of the present invention, the fuel gas circulation flow path includes a purge flow path for discarding exhaust gas from the fuel gas circulation flow path, and the purge flow path includes the fuel gas circulation path. The exhaust gas discarded from the gas circulation channel can be supplied as a heat source to the heat exchanger constituting the steaming mechanism. For this reason, it is possible to use a heat source that normally burns the exhaust gas discarded outside the vehicle to vaporize the generated water, thereby effectively using the exhaust gas.
[0021]
In the fuel cell system according to claim 5 of the present invention, the fuel cell includes an electrolyte membrane / electrode structure in which an anode side electrode and a cathode side electrode are disposed on both sides of a solid polymer electrolyte membrane, a separator, Is a polymer electrolyte fuel cell. Therefore, it is possible to satisfactorily humidify the electrolyte membrane / electrode structure with the steamed generated water, and a dedicated humidifier can be dispensed with. As a result, the entire fuel cell system can be configured economically and compactly.
[0022]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a schematic configuration diagram of a fuel cell system 10 according to a first embodiment of the present invention. The fuel cell system 10 is mounted on a vehicle such as an automobile, and includes a fuel cell stack 12. In the fuel cell stack 12, a plurality of power generation cells 14 are stacked in the direction of arrow A, and end plates 16a and 16b are disposed at both ends in the stacking direction, and the end plates 16a and 16b are stacked in the stacking direction by fastening bolts (not shown). It is tightened to.
[0023]
The power generation cell 14 includes, for example, an electrolyte membrane / electrode structure 18 in which an anode side electrode 18b and a cathode side electrode 18c are arranged on both sides of a solid polymer electrolyte membrane 18a, and a pair sandwiching the electrolyte membrane / electrode structure 18. Separators 20 and 22. The anode side electrode 18b is supplied with, for example, hydrogen gas as a fuel gas, while the cathode side electrode 18c is supplied with, for example, air containing oxygen as an oxidant gas.
[0024]
The end plate 16 a is provided with a hydrogen gas inlet 24 a for supplying hydrogen gas to the power generation cell 14 and an air inlet (oxidant gas inlet) 26 a for supplying air to the power generation cell 14. The end plate 16b has a hydrogen gas outlet 24b for discharging exhaust gas containing unused hydrogen gas discharged from the power generation cell 14 from the fuel cell stack 12, and unused oxygen discharged from the power generation cell 14. An air outlet 26 b is provided for exhausting the contained air from the fuel cell stack 12.
[0025]
The fuel cell system 10 includes a fuel gas supply channel 28 for supplying hydrogen gas to the fuel cell stack 12 and an exhaust gas containing unused hydrogen gas discharged from the fuel cell stack 12. A fuel gas circulation channel 30 for returning to the fuel cell stack 12 and supplying the fuel cell stack 12 and an oxidant gas supply channel 31 for supplying air to the fuel cell stack 12 are provided.
[0026]
The fuel gas supply channel 28 includes a hydrogen tank 32 for storing high-pressure hydrogen, a regulator 34 for reducing the pressure of the hydrogen gas supplied from the hydrogen tank 32, and the reduced hydrogen gas to the fuel cell stack 12. An ejector 36 for supplying exhaust gas from the fuel gas circulation passage 30 and returning it to the fuel cell stack 12 is provided.
[0027]
Between the downstream of the ejector 36 and the fuel cell stack 12, a steaming mechanism, for example, a heat exchanger 38, for steaming the moisture contained in the exhaust gas and passing through the ejector 36 is disposed. In the heat exchanger 38, the mixed hydrogen gas containing the exhaust gas supplied from the fuel gas circulation passage 30 is used as a heating medium, while the compressed air supplied from the oxidant gas supply passage 31 is used as a heating medium (heat source). And the exhaust gas is heated by the compressed air.
[0028]
The oxidant gas supply channel 31 is provided with a supercharger (compressor) 40 for compressing and supplying air, and the oxidant gas supply channel 31 is supplied with fuel via a heat exchanger 38. The battery stack 12 communicates with the air inlet 26a. The air outlet 26b of the fuel cell stack 12 is connected to an air discharge passage 42 for discarding exhaust gas containing unused air to the outside.
[0029]
The operation of the fuel cell system 10 configured as described above will be described below.
[0030]
As shown in FIG. 1, the hydrogen gas supplied from the hydrogen tank 32 to the fuel gas supply passage 28 is depressurized to a predetermined pressure via the regulator 34, and then supplied to the heat exchanger 38 through the ejector 36. . In the heat exchanger 38, as will be described later, the mixed hydrogen gas is heated, and the heated mixed hydrogen gas is supplied to each power generation cell 14 from the hydrogen gas inlet 24a. For this reason, after the mixed hydrogen gas moves along the anode-side electrode 18b constituting each power generation cell 14, exhaust gas containing unused hydrogen gas is discharged from the hydrogen gas outlet 24b to the fuel gas circulation passage 30. The
[0031]
On the other hand, in the oxidant gas supply flow path 31, air is compressed via the supercharger 40, and this compressed air is supplied to the cathode side electrode 28 c of each power generation cell 14 through the heat exchanger 38. The exhaust gas containing unused air is discharged from the air outlet 26b to the air discharge passage 42. Thus, in each power generation cell 14, hydrogen is supplied to the anode side electrode 18b and oxygen in the air supplied to the cathode side electrode 18c reacts to generate power.
[0032]
The exhaust gas discharged to the fuel gas circulation flow path 30 is returned to the fuel gas supply flow path 28 under the suction action of the ejector 36. In this case, as shown in FIG. 2, the liquid produced water 44 contained in the exhaust gas becomes mist-like produced water 44 a by the suction of the ejector 36. Further, the mist-like produced water 44 a passes through the heat exchanger 38, and compressed air is supplied to the heat exchanger 38 under the action of the supercharger 40.
[0033]
The air is heated to a considerably high temperature (for example, 200 ° C.) by being compressed, and is supplied to the heat exchanger 38 as a heat source. For this reason, the mixed hydrogen gas including the hydrogen gas and the exhaust gas supplied to the heat exchanger 38 is heated by high-temperature air that is a heat source as a heating medium. Therefore, the mist-like produced water 44a is converted into water vapor-like produced water 44b by exchanging heat with high-temperature air, and this water-like produced water 44b is supplied to the anode side electrode 18b of each power generation cell 14.
[0034]
Thereby, in 1st Embodiment, the mist-like produced water 44a is supplied in each power generation cell 14, and does not adhere to the anode side electrode 18b, and the water vapor-like produced water 44b uses the anode side electrode 18b. Transmits well. Therefore, hydrogen gas can be reliably supplied to the anode side electrode 18b, and each power generation cell 14 can maintain the desired power generation performance.
[0035]
Furthermore, the air compressed by the supercharger 40 is higher than the operating temperature of the power generation cell 14 that is a solid polymer fuel cell. Therefore, by supplying high-temperature air to the heat exchanger 38 as a heat source, the mist-like generated water 44a is effectively steamed and the high-temperature air that is an oxidant gas is effectively cooled.
[0036]
For this reason, a dedicated humidifier is not required, the heat exchanger 38 and the humidifier are integrated, and the entire fuel cell system 10 can be configured economically and compactly. Moreover, the steam-like generated water 44b can be used as humidified water, and there is an advantage that a dedicated humidifier is not required and the generated water 44 is effectively used.
[0037]
In addition, since the air is rapidly heated under the compression action of the supercharger 40, the response of the heat exchanger 38 is effectively improved, and the generated water is surely steamed immediately after the fuel cell system 10 is operated. Is possible.
[0038]
FIG. 3 is a schematic configuration diagram of a fuel cell system 60 according to the second embodiment of the present invention. The same components as those of the fuel cell system 10 according to the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted. Similarly, in the third embodiment described below, detailed description thereof is omitted.
[0039]
The fuel cell system 60 is provided with a cooling medium inlet 62a for supplying a cooling medium for cooling the power generation cell 14 to the end plate 16b, and the end plate 16a is provided with a high temperature by cooling the power generation cell 14. A cooling medium outlet 62b for discharging the cooling medium is provided.
[0040]
The fuel cell system 60 includes a cooling medium circulation passage 64 that communicates the cooling medium inlet 62 a and the cooling medium outlet 62 b and circulates and supplies the cooling medium along each power generation cell 14. The cooling medium circulation channel 64 is provided with a pump 66 for circulating the cooling medium in the direction of the arrow, and a relatively high-temperature cooling medium discharged from the cooling medium outlet 62b is supplied to the heat exchanger 38 as a heat source. Is done.
[0041]
In the second embodiment configured as described above, the cooling medium is circulated along the cooling medium circulation flow path 64 under the action of the pump 66, and this cooling medium is generated from the cooling medium inlet 62a of the end plate 16b. The power generation cell 14 is cooled by being supplied to the cell 14. The cooling medium having a relatively high temperature by cooling the power generation cell 14 is supplied to the heat exchanger 38 from the cooling medium outlet 62b of the end plate 16b.
[0042]
Thereby, the high-temperature cooling medium discharged from the fuel cell stack 12 can be supplied to the heat exchanger 38 as a heat source, and the generated water in the exhaust gas supplied to the heat exchanger 38 as a heated medium is Heat exchange with the high-temperature cooling medium is performed to reliably convert from a mist state to a water vapor state, and then the fuel cell stack 12 is supplied.
[0043]
Therefore, in the second embodiment, since the water vaporization of the generated water and the cooling of the cooling medium are performed by the single heat exchanger 38, the heat exchange function and the humidification function are integrated, and the fuel cell system 60 as a whole is integrated. Miniaturization can be easily achieved.
[0044]
FIG. 4 is a schematic configuration diagram of a fuel cell system 70 according to the third embodiment of the present invention.
[0045]
In the fuel cell system 70, a three-way valve 72 is provided in the middle of the fuel gas circulation passage 30, and a purge passage 74 for discarding exhaust gas from the fuel gas circulation passage 30 is connected to the three-way valve 72. . The purge flow path 74 supplies exhaust gas as a heat source to the heat exchanger 76, while the heat exchanger 76 is supplied with a mixed hydrogen gas of hydrogen gas and exhaust gas as new fuel gas as a heating medium. .
[0046]
As shown in FIG. 5, the heat exchanger 76 includes a supply port 78 and a discharge port 80, and a plurality of honeycomb structured catalysts 82 are accommodated therein, and a passage 84 meanders along the catalyst 82. Is formed.
[0047]
In the third embodiment configured as described above, when the exhaust gas circulating through the fuel gas circulation passage 30 is discarded (purged) to the outside, the three-way valve 72 is driven and the fuel gas circulation passage 30 is purged. It communicates with the flow path 74. For this reason, the exhaust gas is supplied to the catalyst 82 of the heat exchanger 76 through the purge flow path 74, and catalytic combustion is caused.
[0048]
A mixed hydrogen gas of hydrogen gas and exhaust gas is introduced into the heat exchanger 76 from the supply port 78, and the mixed hydrogen gas is supplied to the fuel cell stack 12 from the discharge port 80 while meandering along the passage 84. At that time, in the heat exchanger 76, the purged exhaust gas is catalytically burned via the catalyst 82, and the mixed hydrogen gas passing through the passage 84 is heated by this catalytic combustion. As a result, the mist component in the mixed hydrogen gas is reliably vaporized and supplied to the fuel cell stack 12.
[0049]
Therefore, in the third embodiment, the exhaust gas that is normally discarded outside the fuel cell system 70 can be combusted and used as a heat source for steaming the generated water, and the exhaust gas can be effectively used. The effect is obtained.
[0050]
【The invention's effect】
In the fuel cell system according to the present invention, the ejector mixes new fuel gas flowing through the fuel gas supply channel with the exhaust gas discharged from the fuel cell, and makes the generated water contained in the exhaust gas into a mist. Furthermore, the mist-like generated water is steamed through a steaming mechanism disposed downstream of the ejector.
[0051]
For this reason, mist-like produced water is supplied into the fuel cell and does not adhere to the anode side electrode, and the vaporized produced water permeates the anode side electrode well. Therefore, the fuel gas can be reliably supplied to the anode side electrode, and the desired power generation performance can be maintained. Moreover, the steamed product water can be used as the humidified water, and a dedicated humidifier is not required, and the product water is effectively used.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of a fuel cell system according to a first embodiment of the present invention.
FIG. 2 is an explanatory diagram of a heat exchanger constituting the fuel cell system.
FIG. 3 is a schematic configuration diagram of a fuel cell system according to a second embodiment of the present invention.
FIG. 4 is a schematic configuration diagram of a fuel cell system according to a third embodiment of the present invention.
FIG. 5 is an explanatory diagram of a heat exchanger constituting the fuel cell system.
6 is a schematic configuration explanatory diagram of a fuel cell power generator according to Patent Document 1. FIG.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10, 60, 70 ... Fuel cell system 12 ... Fuel cell stack 14 ... Power generation cell 16a, 16b ... End plate 18a ... Solid polymer electrolyte membrane 18b ... Anode side electrode 18c ... Cathode side electrode 20, 22 ... Separator 24a ... Hydrogen gas Inlet 24b ... Hydrogen gas outlet 26a ... Air inlet 26b ... Air outlet 28 ... Fuel gas supply passage 30 ... Fuel gas circulation passage 31 ... Oxidant gas supply passage 32 ... Hydrogen tank 36 ... Ejectors 38, 76 ... Heat exchanger 40 ... Supercharger 42 ... Air discharge passage 62a ... Cooling medium inlet 62b ... Cooling medium outlet 64 ... Cooling medium circulation passage 72 ... Three-way valve 74 ... Purge passage 82 ... Catalyst 84 ... Passage

Claims (5)

A fuel cell that is supplied with fuel gas and oxidant gas to generate power; a fuel gas supply channel that supplies the fuel gas to the fuel cell; and an exhaust gas that contains unused fuel gas discharged from the fuel cell. A fuel cell system comprising: a fuel gas circulation channel for returning to the fuel gas supply channel and supplying the fuel cell by an ejector provided in the fuel gas supply channel;
A fuel cell system is provided between the downstream of the ejector and the fuel cell, wherein a water vaporization mechanism for vaporizing water contained in the exhaust gas and passing through the ejector is disposed. The fuel cell system according to claim 1, further comprising an oxidant gas supply channel for supplying the oxidant gas to the fuel cell,
The oxidant gas supply flow path is connected to an oxidant gas inlet of the fuel cell through a heat exchanger constituting the steaming mechanism,
The fuel cell system, wherein the oxidant gas supply flow path is provided with a compressor that sends the compressed oxidant gas as a heat source to the heat exchanger. 2. The fuel cell system according to claim 1, further comprising a cooling medium circulation channel that circulates and supplies a cooling medium to the fuel cell.
The fuel cell system, wherein the cooling medium circulation channel can supply a cooling medium discharged from a cooling medium outlet of the fuel cell as a heat source to a heat exchanger constituting the water vaporization mechanism. 2. The fuel cell system according to claim 1, wherein the fuel gas circulation passage includes a purge passage for discarding exhaust gas from the fuel gas circulation passage.
The fuel cell system, wherein the purge channel is capable of supplying the exhaust gas discarded from the fuel gas circulation channel as a heat source to a heat exchanger constituting the steaming mechanism. 5. The fuel cell system according to claim 1, wherein the fuel cell includes an electrolyte membrane / electrode structure in which an anode-side electrode and a cathode-side electrode are disposed on both sides of a solid polymer electrolyte membrane. 6. And a separator. A fuel cell system, wherein the fuel cell system is a solid polymer fuel cell.

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